1. Field of the Invention
This invention relates to roof constructions and methods of making them, and more particularly, to built-up roof constructions of the shingled-type and which allow for air circulation beneath the shingles to forestall deterioration. The invention has particular utility and applicability to roofs (and the making of roofs) using wooden shingles, such as cedar shakes, applied over wooden or wood-based sheathing.
2. Description of the Prior Art
It is well known that moisture from the interior of a building structure, as well as water leaking through the outer structure of a built-up roof construction, may accumulate in the roof structure and cause rapid deterioration and ultimately failure. The problem of accumulated moisture is especially serious in roofs using potentially biodegradable materials, such as wooden shingles.
In conventional high quality wooden roof constructions, one by three inch furring strips are applied, in spaced rows about five inches apart, to the sheathing or decking, typically plywood or particle board, in a direction transverse to the pitch of the roof. The shingles, such as cedar shakes, are applied to the furring strips and spaced from the sheathing or decking by the thickness of the strips. Thus, the furring strips serve to space the shingles from the sheathing and allow the structure to "breathe" in the sense of allowing for the circulation of air beneath the shingles to remove moisture.
Because the application of furring strips is time consuming and relatively exacting work, many wooden shingled roofs are currently being made with shakes applied directly to the decking, in a manner which precludes or at least greatly impedes the circulation of air beneath the shakes. Such constructions encourage the shakes to rot, and accelerate roof failure. Indeed, common understanding in the building industry is that a wooden roof in which the cedar shakes are applied directly to the sheathing has a life expectancy of only seven to eight years.
Ventilated built-up roof constructions have heretofore been proposed.
U.S. Pat. No. 4,538,388, issued Sept. 3, 1985, to Friesen, discloses a roof structure which uses a plastic film and spaced vents to allow for ventilation of water vapors within or seeking entry to the roof system.
U.S. Pat. No. 4,805,367, issued Feb. 21, 1989, to Klechner, suggests a circulation enhancing support between a roof deck and roof insulation, the support being a screen or grid-like structure made up of regular sets of spaced apart undulating elements joined with other such elements, as by welding.
U.S. Pat. No. 4,315,392, issued Feb. 16, 1982, to Sylvest, discloses a built up roof, which comprises sheathing, over which is disposed a roof covering sheet material spaced from the sheathing, and a spacing means made up of a mat of resilient nonwoven wires, threads or fibers of high air volume.
Many other ventilated roof constructions and roofing materials have been proposed.